1. Field of the Invention
The present invention relates to a method of in-situ strengthening of existing pipes, and more particularly to a method for strengthening pipes by installing a reinforced composite inside the pipe, comprising a helically wound tensile reinforcement material.
2. Background of the Prior Art
Buried pipe infrastructure is rapidly deteriorating throughout the world. Many pipes transmit water and waste in gravity flow conditions, while other pressurized pipes are subject to large internal hydrostatic pressures. Pipes are generally made from steel, reinforced concrete, or polymer materials, including fiber reinforced polymers. Many pressure pipes are constructed of steel and concrete and prestressed with external wire, wrapped helically around the exterior circumference of the pipe. These wires are coated with an additional layer of concrete for corrosion protection. Pipes exposed to aggressive environments deteriorate over time due to corrosion or other material processes depending upon the materials of which they are constructed. After substantial deterioration has taken place, the pipes are required to be replaced or repaired. In the case of pressure pipes, failure can result in expensive and dangerous main breaks. The reinforcing prestressed wires are subject to deterioration and breakage resulting in pipe failure. External pressure from the surrounding environment and internal pressure from the water they carry may cause the pipes to crack and leak. In order to repair the pipes, segments must typically be removed entirely requiring significant disruption to traffic and structures above the pipes, such as roads or buildings. In addition, such repairs consume significant amounts of time and resources, and can be quite costly.
There are many different in-situ methods for repairing failed or deteriorating pipes. Some methods are intended to strengthen the existing pipe, relying on some strength being contributed by the existing pipe, while others are intended to entirely replace the existing pipe. Some of such methods include placing liners inside the pipe and adhering such liners to the pipe's internal walls as shown, for example, in U.S. Pat. Nos. 3,149,646; 4,768,562; 5,308,430; 6,089,275; 6,167,913; 6,283,211; 7,025,580; 7,258,141; 7,267,739; and United States Patent Application Publication No. 2008/0178955. Other methods used for repairing such pipes place materials around the structure on the outside wall of the pipe to protect and reinforce the pipe as shown, for example, in U.S. Pat. No. 5,683,530. The currently existing methods of lining or reinforcing pipes are labor intensive and expensive.